This invention relates to a mechanical knee for converting the weight of the wearer to a knee extensor force.
Recent studies on the biomechanics of the knee have revealed new insights regarding the extension mechanism. The role of the patella as a pulley mechanism has never been fully clarified. However, the study of muscle activity in the thigh muscles has revealed that the real function of the musculature is to elevate the thigh with the body weight over the planted lower extremity rather than just to extend the knee during the swing phase of gait. In addition the musculature prevents the collapse of the flexed knee during weight bearing.
With existing prosthetic legs extension is obtained by utilization of centrifugal force when the patient swings the leg forward before weight bearing. This extension may be assisted by an elastic strap on the front of the prosthesis. With this prosthesis, extension must be obtained before weight is applied.
The invention provides a mechanical knee for use with either a prosthetic lower leg or with a leg brace. The mechanical knee utilizes a pulley and an eccentric connection between the pulley and the upper leg to convert the weight of the wearer to a rotational force on the pulley. The rotational force of the pulley acts on a bar which extends between the pulley and the upper leg and creates an extensor force on the upper leg. The mechanical knee converts weight bearing to a knee extensor force without having to swing the lower leg.